15267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles)/* 25267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) * Copyright (C) 2013 Google Inc. All rights reserved. 35267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) * 45267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) * Redistribution and use in source and binary forms, with or without 55267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) * modification, are permitted provided that the following conditions are 65267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) * met: 75267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) * 85267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) * * Redistributions of source code must retain the above copyright 95267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) * notice, this list of conditions and the following disclaimer. 105267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) * * Redistributions in binary form must reproduce the above 115267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) * copyright notice, this list of conditions and the following disclaimer 125267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) * in the documentation and/or other materials provided with the 135267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) * distribution. 145267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) * * Neither the name of Google Inc. nor the names of its 155267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) * contributors may be used to endorse or promote products derived from 165267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) * this software without specific prior written permission. 175267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) * 185267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 195267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 205267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 215267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 225267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 235267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 245267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 255267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 265267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 275267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 285267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 295267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) */ 305267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) 315267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles)#include "config.h" 325267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) 335267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles)#if ENABLE(WEB_AUDIO) 345267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) 351e202183a5dc46166763171984b285173f8585e5Torne (Richard Coles)#include "platform/audio/DownSampler.h" 365267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) 375267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles)#include "wtf/MathExtras.h" 385267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) 39c1847b1379d12d0e05df27436bf19a9b1bf12deaTorne (Richard Coles)namespace blink { 405267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) 415267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles)DownSampler::DownSampler(size_t inputBlockSize) 425267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) : m_inputBlockSize(inputBlockSize) 435267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) , m_reducedKernel(DefaultKernelSize / 2) 44f79f16f17ddc4f842d7b7a38603e280e94be826aTorne (Richard Coles) , m_convolver(inputBlockSize / 2) // runs at 1/2 source sample-rate 455267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) , m_tempBuffer(inputBlockSize / 2) 465267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) , m_inputBuffer(inputBlockSize * 2) 475267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles){ 485267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) initializeKernel(); 495267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles)} 505267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) 515267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles)void DownSampler::initializeKernel() 525267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles){ 535267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) // Blackman window parameters. 545267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) double alpha = 0.16; 555267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) double a0 = 0.5 * (1.0 - alpha); 565267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) double a1 = 0.5; 575267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) double a2 = 0.5 * alpha; 585267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) 595267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) int n = DefaultKernelSize; 605267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) int halfSize = n / 2; 615267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) 625267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) // Half-band filter. 635267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) double sincScaleFactor = 0.5; 645267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) 655267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) // Compute only the odd terms because the even ones are zero, except 665267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) // right in the middle at halfSize, which is 0.5 and we'll handle specially during processing 675267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) // after doing the main convolution using m_reducedKernel. 685267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) for (int i = 1; i < n; i += 2) { 695267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) // Compute the sinc() with offset. 705267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) double s = sincScaleFactor * piDouble * (i - halfSize); 715267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) double sinc = !s ? 1.0 : sin(s) / s; 725267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) sinc *= sincScaleFactor; 735267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) 745267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) // Compute Blackman window, matching the offset of the sinc(). 755267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) double x = static_cast<double>(i) / n; 76d5428f32f5d1719f774f62e19147104ca245a3abTorne (Richard Coles) double window = a0 - a1 * cos(twoPiDouble * x) + a2 * cos(twoPiDouble * 2.0 * x); 775267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) 785267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) // Window the sinc() function. 795267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) // Then store only the odd terms in the kernel. 805267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) // In a sense, this is shifting forward in time by one sample-frame at the destination sample-rate. 815267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) m_reducedKernel[(i - 1) / 2] = sinc * window; 825267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) } 835267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles)} 845267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) 855267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles)void DownSampler::process(const float* sourceP, float* destP, size_t sourceFramesToProcess) 865267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles){ 875267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) bool isInputBlockSizeGood = sourceFramesToProcess == m_inputBlockSize; 885267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) ASSERT(isInputBlockSizeGood); 895267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) if (!isInputBlockSizeGood) 905267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) return; 915267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) 925267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) size_t destFramesToProcess = sourceFramesToProcess / 2; 935267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) 945267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) bool isTempBufferGood = destFramesToProcess == m_tempBuffer.size(); 955267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) ASSERT(isTempBufferGood); 965267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) if (!isTempBufferGood) 975267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) return; 985267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) 995267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) bool isReducedKernelGood = m_reducedKernel.size() == DefaultKernelSize / 2; 1005267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) ASSERT(isReducedKernelGood); 1015267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) if (!isReducedKernelGood) 1025267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) return; 1035267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) 1045267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) size_t halfSize = DefaultKernelSize / 2; 1055267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) 1065267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) // Copy source samples to 2nd half of input buffer. 1075267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) bool isInputBufferGood = m_inputBuffer.size() == sourceFramesToProcess * 2 && halfSize <= sourceFramesToProcess; 1085267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) ASSERT(isInputBufferGood); 1095267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) if (!isInputBufferGood) 1105267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) return; 1115267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) 1125267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) float* inputP = m_inputBuffer.data() + sourceFramesToProcess; 1135267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) memcpy(inputP, sourceP, sizeof(float) * sourceFramesToProcess); 1145267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) 1155267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) // Copy the odd sample-frames from sourceP, delayed by one sample-frame (destination sample-rate) 1165267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) // to match shifting forward in time in m_reducedKernel. 1175267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) float* oddSamplesP = m_tempBuffer.data(); 1185267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) for (unsigned i = 0; i < destFramesToProcess; ++i) 1195267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) oddSamplesP[i] = *((inputP - 1) + i * 2); 1205267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) 1215267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) // Actually process oddSamplesP with m_reducedKernel for efficiency. 1225267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) // The theoretical kernel is double this size with 0 values for even terms (except center). 1235267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) m_convolver.process(&m_reducedKernel, oddSamplesP, destP, destFramesToProcess); 1245267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) 1255267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) // Now, account for the 0.5 term right in the middle of the kernel. 1265267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) // This amounts to a delay-line of length halfSize (at the source sample-rate), 1275267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) // scaled by 0.5. 1285267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) 1295267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) // Sum into the destination. 1305267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) for (unsigned i = 0; i < destFramesToProcess; ++i) 1315267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) destP[i] += 0.5 * *((inputP - halfSize) + i * 2); 1325267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) 1335267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) // Copy 2nd half of input buffer to 1st half. 1345267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) memcpy(m_inputBuffer.data(), inputP, sizeof(float) * sourceFramesToProcess); 1355267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles)} 1365267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) 1375267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles)void DownSampler::reset() 1385267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles){ 1395267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) m_convolver.reset(); 1405267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) m_inputBuffer.zero(); 1415267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles)} 1425267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) 1435267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles)size_t DownSampler::latencyFrames() const 1445267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles){ 1455267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) // Divide by two since this is a linear phase kernel and the delay is at the center of the kernel. 1465267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) return m_reducedKernel.size() / 2; 1475267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles)} 1485267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) 149c1847b1379d12d0e05df27436bf19a9b1bf12deaTorne (Richard Coles)} // namespace blink 1505267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles) 1515267f701546148b83dfbe1d151cb184385bb5c22Torne (Richard Coles)#endif // ENABLE(WEB_AUDIO) 152